GC680 Waste water vent/breather

[IsThisNameLongEnough]

Does anyone know where the vent pipe for the waste water tank is / goes to / is there one fitted?

We are having two odd issues:
- There is a persistent 'manky' smell in the bathroom, even with a fresh clean toilet / shower not been used. (Note we have removed the bungs from the shower floor)

- When draining the waste/gray water tank on our GC680 - have noticed that it only drained down to about 15%, and reasonably slowly at that. Have tried flushing the tank with a little success, but the shower drain 'burped' while doing this - and had the same manky smell


This makes me suspicious that the tank vent is blocked, so was just wondering where this is from factory?
Or - if there is no vent on the tank from factory - whether VW NZ have done a hack job of putting this in for certification (gray water tanks required to be vented in New Zealand)

 

[GordonH]

There is a breather on the tank you could check as the traps shouldn’t ’burp’ when you empty the tank. If you have removed the plugs from the shower and there is no water in those traps (or the sink trap) then you will get odour from the grey waste tank. Even if you dont use the shower it’s best to keep refreshing the trap water to stop that going stale. using suitable grey waste tank cleaner and pouring a little down all the traps in the van from time to time is a good idea. We use this - Elsan Fresh 2 Waste Water Tank Additive, Grey, 2 Litre https://amzn.eu/d/h2Nvj73

 

[Carryon Cali Camping]

Agree with what @GordonH has said above. We also pour Elsan Tank additive down our plug holes from time to time. When not in use, we also keep the waste water drain valve open for air flow etc.
If you want to give the tank a clean, I have 3/4 filled the tank (on a previous Motorhome) including some tank cleaner and gone for a drive to give it a good swill around, left it for a few hours and then drained.